In the FPD industry ever larger sheets of glass are being employed in the manufacture of Flat Panel Displays. The processing of these sheets is expensive in that their increasing size makes handling difficult regarding the brittle nature of the glass, due to its thin cross section—precluding anything but the gentlest method of transference. Because the required surface finish is intolerant of any type of defect or contamination manufacturers are increasingly moving towards non-contact conveyance of the panels in handling and processing in order to increase the yield rate. The manufacturing process of the substrate sheets of glass require many operations to before they can be integrated with other components. In order for the substrates to perform properly, they must be processed to a high degree of accuracy. This would include coating without contamination, streaking and marks, drying, and either coating any number of different ways, and or baking to finish a particular process correctly without blemish or defect. Further increasing the difficulty in processing is the need to perform some operations in a vacuum environment to insure non-contamination of the coating process.
Because the handling and processing of FPD glass is so similar to wafers and circuit boards and other elements inherent in the semi-conductor industry, it is anticipated by the inventor that this method and/or apparatus and invention is directly transferable and translatable to the semiconductor industry and its attendant requirements of manufacturing production. Also the usefulness of the invention when processing flexible film substrates and webs in a continual method should be readily apparent.
Coating
Various means of coating are employed in industry. A common method for coating is to pass the substrate beneath a curtain of material which deposits a material upon the substrate in a random orientation and thickness, or to have a type of “Shower head” which deposits an even layer of material on the substrate. This is unsatisfactory since the thickness of the coating and the processing parameters need to be controlled for precision applications, also since the size of the apparatus required for ever larger generations of glass is prohibitive, since such equipment must be operated in a clean room environment in order to prevent contamination from particles. Substrates can be dipped and or sprayed as well—neither of which is suitable for FPD glass, or semi-conductor industry products due to handling issues and a lack of assurance of non-contamination. Still a common further method is the use of “Chemical Vapor Deposition” where a substrate is placed within a chamber containing a heater in a vacuum environment which heats up and evaporates the coating material to be applied. Subsequently the evaporated material settles on all the surfaces of the chamber, which include the substrate material to be coated. Very precise thickness coatings can be attained in this manner, however the size of the FPD glass, and some Integrated Circuits and wafers pose a problem regarding the subsequent size of the vacuum vessel needed to accommodate these substrates. Also, the processing time required to create the vacuum environment for larger panels is deleterious to lower cost processing and ease of application. This process also must take place in a clean room, the floor space for which is expensive.
Drying & Baking
During a cleaning process involving water upon a substrate or device requiring such high tolerances as are required in the FPD and semiconductor industries the substrate will need to be dried. Critical to this process is no remaining moisture on the surface, and also to insure that there is no streaking and or impurities remaining on the surface of the substrate due to their presence in the cleaning solution which has then evaporated away, leaving them behind. Further, there are some processes within the aforementioned industries that require a baking process. This entails a higher order of heat and or application of radiant heat and light to enhance a process, or complete a curing of a coating, or similar elements.
Conventional drying for FPD glass involves heating and placing the substrate within a chamber and causing the substrate to dwell there, while a heat source is applied to remove any moisture. Problems associated with un-even heating arise in that if the heat source is not applied evenly to the substrate surface, warping and or variations in the surface quality can occur, as well as areas where there is more rapid evaporation of the rinse water from the cleaning process, leaving behind streaks and or water spots.
Still further, baking presents problems to the cleanliness of the clean room environment, since the presence of high heat sources can create unwanted particulate and contamination in clean room environments through the opening and closing of the chamber used to heat the substrates.
Within the semi-conductor industry discreet chambers are used where the wafers can be dried, or baked. The substrate must be moved to those chambers. Likewise in the FPD market, drying is usually accomplished as part of the cleaning process in separate drying and baking chambers.